Containers, disposable tableware and packages are made of paperboard by means of a technique comprising the following typical stages of operation: cutting a blank from a board web, folding and/or bending and joint sealing the blank to give the item being made its final shape. Paperboard containers and plates are also produced by press-moulding or deep-drawing the blank. Other moulding machining operations of paperboard products include providing paperboard containers, such as cups and mugs, with a rolled-up or creased rim or a so-called mouth roll, and forming annular reinforcing ribs or similar creases on the sides of the paperboard vessels or packages.
In the press moulding of paperboard articles, the blank is brought between a pair of heated press moulds, whereby the paperboard bends or folds under compression, forming creases on the rim or in the corners of the article thus formed. Heating is necessary to make the deformation of the paperboard permanent. Press moulding has been used in the manufacture of foodstuff dishes and plates made of paperboard in particular.
The purpose of the mouth roll that is formed on paperboard drinking cups and mugs, on the one hand, is to stiffen the cup and, on the other hand, to provide the desired touch with the user's mouth, when enjoying a beverage. The mouth roll is provided by a tool that bends and/or presses the paperboard, mostly at the final stage of manufacture of a cup that is already bent and sealed. To make the mouth roll sufficiently tight and permanent, a heated tool is used, as well as additives, such as oils, and moistening of the paperboard. However, as fluctuations in the moisture of air have an effect on it, the moistening of the paperboard in particular is difficult to control in practice; in addition, moistened paperboard tends to warp or, when becoming too damp, completely loses its stiffness.